VEC tuning questions

[gen 3 motorsports]

Hey all. I have this Roe s/c tuned up pretty nice now. Runs very well and consistent. Still a couple tiny gliches to try and fix. Can someone tell me what conditions define PE/WOT? At what TPS %, etc. What I see on my wideband is when I slightly accelerate from say a slow speed of 30mph at 2krpm tps around 20%. then when I roll the throttle up to maybe 35% a little abruptly the AFR will dump to 11.5 from stoic like its going into power enrichment mode. This sometimes causes a little hiccup. Otherwise, I've balanced out the cyl-to-cyl fueling nicely (8, 9, 10 were pig rich at first), car runs awesome.

Also, I have not been able to enable the VEC scanner to read the internal MAP/boost. I've configured each of the Analog In and Out's to try and show this reading on a scan, no luck.

I actually have the car tonight (Sunday) and would like to wrap up the tuning, hence this post. Otherwise I will call Roe in the AM. Thanks for any input.

Robert

[Jack B]

The a/f readings are meaningless when going on/off throttle. One question, how did you know that three cylinders were running rich

[gen 3 motorsports]

Originally Posted by Jack B

The a/f readings are meaningless when going on/off throttle. One question, how did you know that three cylinders were running rich

Jack; I'm not talking about any kind of decel mode. This is acceleration, then a little more acceleration, going from 25% tps to 35-40% tps seems to dump the regime into PE/open loop mode. This is why I am trying to figure out what the stock computer defines as PE vs stoichiometric. On the C5s PE/wot/open loop is defined by a certain TPS position and RPM. I can change those setpoints with HP Tuners or LS1Edit to enable PE sooner or later in TPS at any rpm.

Fouling plugs: Immediately after the s/c and VEC install I was fouling plugs, but only on the back 4 cylinders (7,8,9,10). I noticed the VEC software had individual offsets for each injector. After talking to Roe and other Viper tuners it seems the shallow/short runners on the intake manifold do not disperse air evenly front to rear; rears get less air. This is exacerbated by the s/c I guess. So this explained why these 4 cyls were blacker than a bag of assholes while the other 6 plugs looked real good. The VEC has offset adjustment you can make to individual injector pulse width. One bank slave's off the others, too. So after several tuning changes along with new plugs I finally got the motor balanced. Then I tuned the fuel curve globally with the other tables in VEC2. Car runs REALLY good. I am very impressed. I just need to fix the occasional slight stumble during light accel like I described above.

[KenH]

On the MAP sensor, I have mine setup on 'AN3 In' (master) using sensor 'MPX US 2'.

On the TPS voltage required to go into open loop mode, I think it has to be a fairly high voltage of > 4.4V, because when my TPS wasn't reading over 4.4V, the PCM wasn't going into open loop mode even at WOT. Once I got it adjusted up around 4.8V, it would go into open loop mode at WOT.

[gen 3 motorsports]

Hey Ken;

As usual, I can count on you for good input man!! Thanks!! I also tried to set up AN3 In on MPX US 2, just like you, but I dont register any change during scanning, just a steady line. I have tried every combo of AN1-3 In and Out on PMX US 2 and on Bar. WTF? I guess I will have to wait until Tues morning to talk to Roe.

I will double check the TPS to see where in the physical travel of the throttle I am achieving the higher voltage regimes of the TPS sensor.

Robert